FR3101409A3 - Spacer element for heat exchanger - Google Patents

Abstract

The invention relates to an intermediate element (1, 2) for a heat exchanger comprising at least a first corrugated structure (1) and a second corrugated structure (2) each comprising a succession of fins (123, 223) connected alternately by means of wave tops (121, 221) and wave bases (122, 222). According to the invention, said first and second corrugated structures are nested within each other. Abstract figure: Fig. 3

Description

Spacer element for heat exchanger

The invention relates to an intermediate element for a heat exchanger as well as a heat exchanger of the brazed plate and fin type comprising such an intermediate element.

The technology commonly used for an exchanger is that of brazed aluminum plate and fin or wave exchangers, which make it possible to obtain very compact devices offering a large exchange surface.

These exchangers include separating plates between which are inserted heat exchange structures, generally corrugated or wave structures, formed of a succession of fins or wave legs, thus constituting a stack of passages for the different fluids to be placed. in heat exchange relationship.

Intermediate elements are generally arranged in the passages of the exchanger. These heat exchange structures are in the form of a corrugated product, or heat exchange waves, comprising fins, or wave legs, which extend between the plates of the exchanger and allow the surface area to be increased. heat exchange of the exchanger. The intermediate elements are assembled to the plates by brazing.

Currently, the spacer elements of plate and wave heat exchangers are manufactured mainly using two techniques.

One technique is forming. This technology consists of bending an aluminum strip of a certain thickness using a press and a tool. This technique is known and mastered. However, it has certain limits linked in particular to the design of the tools used to form the waves, which most often consist of blades assembled one beside the other. The denser the wave to be formed, that is to say the greater the number of fins per unit length, the thinner and more fragile these blades are. The higher the waves, the higher the blades. The risk of breakage of the tool blade is greater the thicker the strip and the thinner and taller the blade. The density and height of the waves are therefore limited by the thickness of the aluminum strip used and there is a maximum thickness / density pair for each type of corrugated structure.

Another technique is the switch to the dial. This technology consists of passing an aluminum strip between several series of toothed wheels. The latter gradually deform the aluminum strip until the desired density and height of corrugation are obtained. The use of toothed wheels, however, induces waves with wavelengths having a non-zero angle with respect to the vertical, generally greater than 5 °. In addition, the tolerances in terms of height are greater than those obtained by forming, which can pose a problem during brazing.

In order to increase the density of the waves and / or the thickness of the legs of the waves, which may be necessary in some processes to maximize heat exchange, the corrugated structures can be machined, molded or cast. However, these techniques are either very time consuming and expensive, or poorly suited to the production of high precision parts required for assembly.

The problem to be solved is to provide an intermediate element for a heat exchanger, the density, thickness and / or height of which can be increased without complicating the manufacture or running the risk of breaking the manufacturing tools .

The solution according to the invention is then an intermediate element for a heat exchanger comprising at least a first corrugated structure and a second corrugated structure each comprising a succession of fins connected alternately by wave tops and wave bases, characterized in that said first and second corrugated structures are nested one inside the other.

Depending on the case, the invention may include one or more of the following characteristics:

• the fins of the first structure and the fins of the second corrugated structure follow one another in a first direction and respectively have a first thickness and a second thickness, said first and second thicknesses being measured parallel to the first direction, the second thickness being less than the first thickness.
• the first corrugated structure and the second corrugated structure respectively have a first pitch and a second pitch, said first and second pitch being defined as the distances between two successive fins of the same corrugated structure measured along the first direction, the first pitch and / or the second pitch being variable.
• the first corrugated structure and the second corrugated structure respectively have a first density of fins and a second density of fins, said first and second densities of fins being defined as the number of fins per unit length of the same structure wavy, measured in the first direction, the first density being less than the second density.
• a layer of brazing agent is interposed between the first corrugated structure and the second corrugated structure.
• the spacer further comprises a third corrugated structure, the first corrugated structure, the second corrugated structure and the third corrugated structure being nested within each other, with the first corrugated structure arranged between the second corrugated structure and the third corrugated structure .

Furthermore, the invention relates to a heat exchanger of the brazed plate and fin type comprising a plurality of plates arranged parallel to one another so as to define a series of passages for the flow of a first fluid to be brought into contact with each other. heat exchange with at least a second fluid, and at least one intermediate element according to the invention arranged between two successive plates so as to form, within the passage defined between the two plates, several channels for the flow of the first fluid.

The invention will now be better understood thanks to the following description, given solely by way of non-limiting example and made with reference to the appended figures, among which:

represents a first wave according to an embodiment of the invention.

represents a second wave according to an embodiment of the invention.

represents an intermediate element comprising a first wave and a second wave according to one embodiment of the invention.

represents an intermediate element according to another embodiment of the invention.

Figure 1 shows schematically a first corrugated structure 1 comprising a succession of fins 123 connected alternately by wave tops 121 and wave bases 122. The fins 123 follow one another in a first direction. The fins 123 extend generally in a second direction, orthogonal to the first direction, and which generally corresponds to the direction of flow of the first fluid flowing in the exchanger passage within which the structure is arranged. The fins 123 have a first thickness, measured in the first direction, corresponding to the thickness of the strip previously used to form the structure. The wave tops and bases 121, 122 have the same thickness as the fins 123.

FIG. 2 is a diagram of a second corrugated structure 2 to which the characteristics described above can be transposed for the first structure.

Figure 3 shows an interlayer formed by nesting the first corrugated structure 1 and the second corrugated structure 2 within each other. In other words, the wave tops, wave bases and fin of the structures are shaped so that they overlap, the surfaces of the second structure oriented and of the first structure oriented towards each other forming complementary. Preferably, a brazing agent layer is arranged between the corrugated structures to join them together.

The proposed solution provides the possibility of greatly increasing the thickness and density of the resulting spacer, while continuing to manufacture each corrugated structure by conventional forming, limiting or even avoiding the risk of breakage of the forming tools. The inventors of the present invention have thus demonstrated a gain of 30 to 40% in the thickness of the intermediate element and of (50 to 100% in its density.

Preferably, the fins of the first corrugated structure follow each other periodically, that is to say that the pitch of the structure, defined as the distance between two successive fins of the same corrugation, measured in the first direction, is constant . The first structure can also be produced with a variable pitch if necessary.

Preferably, the fins of the first corrugated structure have a greater thickness than the thickness of the fins of the second corrugated structure.

Preferably, the first corrugated structure has a density of fins greater than that of the second corrugated structure.

Preferably, the second corrugated structure has a variable pitch so that it can interlock with the first corrugated structure.

Note that two to three strips, or even more, can be used to form the spacer.

Thus, FIG. 4 shows schematically an intermediate element formed from three strips, the strips being shaped beforehand to form a first corrugated structure 1, a second corrugated structure 2 and a third corrugated structure 3. An additional aluminum strip large thickness is used to form the first corrugated structure 1 in a conventional manner. Two thinner strips, each coated on one side with solder, are used to produce waves of higher density. These structures 2, 3 have a variable pitch in order to be able to fit into the very thick structure 1.

Preferably, the corrugated structure (s) of smaller thicknesses forming the intermediate element have the finest fins, that is to say requiring the thinner blades. Given the thinness of the strip used, the thinness of the blade does not increase the risk of tool breakage. We can also play with the annealing state of the alloys used. This is because the forming of aluminum is easier as the alloy is strongly annealed. This is characterized by a greater elongation at break which avoids the risk of tearing the strip. The small thickness corrugated structures could therefore be made from an annealed alloy. The corrugated structures will be coated with a brazing agent which may be the same as that used to braze the vacuum exchangers. This will allow the corrugated structures of waves to be joined together for mechanical strength.

As corrugated structures, we can use the different types of waves usually implemented in exchangers of the brazed plate and fin type. The waves can be chosen from known wave types such as straight waves, so-called partially offset waves (of the "serrated" type), wave waves or herringbones (of the "herringbone" type). . These waves may or may not be perforated.

Claims (7)

Intermediate element for a heat exchanger comprising at least a first corrugated structure (1) and a second corrugated structure (2) each comprising a succession of fins (123, 223) connected alternately by wave tops (121, 221) and wave bases (122, 222), characterized in that said first and second corrugated structures are nested one within the other. Intermediate element according to Claim 1, characterized in that the fins (123) of the first corrugated structure (1) and the fins (223) of the second corrugated structure (2) follow one another in a first direction and respectively have a first thickness and a second thickness, said first and second thickness being measured parallel to the first direction, the second thickness being less than the first thickness. Intermediate element according to one of Claims 1 or 2, characterized in that the first corrugated structure (1) and the second corrugated structure (2) respectively have a first pitch and a second pitch, said first and second pitch being defined as the distances between two successive fins (123, 223) of the same corrugated structure measured in the first direction, the first pitch and / or the second pitch being variable. Intermediate element according to one of claims 1 to 3, characterized in that the first corrugated structure (1) and the second corrugated structure (2) respectively have a first density of fins and a second density of fins, said first and second fin densities being defined as the number of fins (123, 223) per unit length of the same corrugated structure, measured in the first direction, the first density being less than the second density. Intermediate element according to one of claims 1 to 4, characterized in that a layer of brazing agent is interposed between the first corrugated structure (1) and the second corrugated structure (2). Intermediate element according to one of claims 1 to 5, characterized in that it further comprises a third corrugated structure (3), the first corrugated structure (1), the second corrugated structure (2) and the third corrugated structure ( 3) being nested in each other, with the first corrugated structure (1) arranged between the second corrugated structure (2) and the third corrugated structure (3). Heat exchanger of the brazed plate and fin type comprising a plurality of plates arranged parallel to one another so as to define a series of passages for the flow of a first fluid to be placed in a heat exchange relationship with at least one second fluid , and at least one intermediate element arranged between two successive plates so as to form, within the passage defined between the two plates, several channels for the flow of the first fluid, characterized in that the intermediate element is according to one of claims 1 to 6.